1. Field of the Invention
The present invention relates to power screw type disc brakes and more particularly to power screw type disc brakes having internal force or clearance sensing automatic, single acting (i.e. operates automatically in the slack take-up direction only) slack adjusters.
2. Brief Description of the Prior Art
Power screw type disc brakes of the type wherein rotation of an externally threaded shaft, known as the power screw, acts upon an internally threaded member, known as the power nut, to apply a clamping force to the friction material on one or both sides of a brake disc are well known in the prior art. Examples of such power screw disc brakes may be seen by reference to U.S. Pat. Nos. 3,976,168; 4,014,411; 4,022,300; 4,036,330 and 4,050,549, the disclosures of which are all hereby incorporated by reference.
Several of the prior art power screw disc brakes utilize external slack adjusters of the manual or automatic type. Such external slack adjusters were typically incorporated into the lever arms by which rotational movement was applied to the power screw and were often identical or substantially identical to automatic slack adjusters utilized for "S" cam expanding shoe drum brakes. Examples of such external slack adjusters are well known in the prior art and may be seen by reference to U.S. Pat. Nos. 3,507,369; 3,901,357; 4,256,208 and 4,351,419 the disclosures of all of which are hereby incorporated by reference.
Other designs of the prior art power screw type disc brakes utilize internal automatic slack adjusters of both the force sensing and the stroke sensing type. Examples of such prior art power screw disc brakes may be seen by reference to the above-mentioned U.S. Pat. Nos. 3,976,168 and 4,014,411.
The prior art power screw d.sc brakes utilizing stroke sensing automatic slack adjusters, both of the internal and external type, were not totally satisfactory as stroke sensing automatic slack adjusters tend to overadjust the brakes. The prior art power screw disc brakes utilizing external slack adjusters, of both the stroke sensing and clearance sensing type, were not totally satisfactory as the slack adjuster was not enclosed and protected within the disc brake mechanism and as the disc brake mechanism could not be specifically designed for a specific type of automatic slack adjuster.
The prior art power screw disc brakes utilizing internal automatic slack adjusters of the clearance sensing type minimize many of the drawbacks of the above mentioned types of power screw disc brakes but were not totally satisfactory as the structure of the automatic slack adjustment mechanism tended to be rather complicated, expensive to produce, require an undesirably large amount of space, difficult to maintain, difficult to manually backoff and/or less reliable than desired.